摘要
地下介质中普遍存在各向异性及黏滞性,各向异性会使地震波走时发生变化,黏滞性会使地震波发生振幅衰减和相位畸变.在进行地震资料偏移成像时,忽略介质各向异性及黏滞性的影响会导致绕射波不收敛、构造位置不准确,能量不均衡,偏移剖面频带变窄等问题,大幅降低偏移剖面质量.本文基于TI介质纯qP波动方程,结合常Q模型的松弛函数,推导出新的黏声各向异性纯qP波动方程.在该方程中,振幅衰减项与相位频散项是解耦的,因此利用该方程进行成像时,可通过改变振幅衰减项的符号进行衰减补偿.多个数值算例结果表明文中所提出的方程可以正确描述地震波在各向异性衰减介质中的传播特征,应用本文方程进行成像时能够有效校正各向异性及黏滞性对偏移剖面的影响,提高成像剖面的分辨率及精度.
Anisotropy and viscosity are common in subsurface media. Anisotropy will change the seismic wave travel-time, and viscosity will cause amplitude attenuation and phase distortion. In the migration process, it will lead to kinds of problems ignoring the influence of media anisotropy and viscosity. For example, it will cause diffracted wave not converge and inaccurate structural position if taking no account of the media anisotropy. In addition, it will result in energy imbalance and narrowing seismic wave frequency band in migration profile without absorption and attenuation compensation during imaging. All these problems will substantial reduce the quality and resolution of migration profiles. Therefore, based on the pure qP-wave equation in TI media and the relaxation function of constant Q model, a new viscoacoustic anisotropic pure qP-wave equation is derived in this paper. In the new equation, amplitude attenuation term and phase dispersion term are decoupled. Then the attenuation compensation can be carried out easily by changing the sign of the amplitude attenuation term and leaving the sign of the dispersion term unchanged when imaging with the decoupled viscoacoustic pure qP-wave equation in TI media. We tested the equation and RTM approach on several models and numerical results showed that the proposed equation can correctly describe seismic wave propagation characteristics in anisotropic attenuation media. As a result, the Q-compensated migration based on the proposed equation can effectively correct the influence of anisotropy and viscosity and improve the resolution of imaging profile.
作者
张闪闪
谷丙洛
丁奕文
王霁川
李振春
ZHANG ShanShan;GU BingLuo;DING YiWen;WANG JiChuan;LI ZhenChun(Key Laboratory of Deep Oil and Gas,China University of Petroleum(East China),Qingdao 266580,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2022年第10期4047-4062,共16页
Chinese Journal of Geophysics
基金
国家自然基金项目(42004093,42074133)
山东省自然基金项目(ZR2020QD050)联合资助。
关键词
各向异性
衰减补偿
近似常Q模型
纯qP波
逆时偏移
Anisotropic
Attenuation and compensation
Nearly constant Q model
Pure qP-wave
RTM
